Histidine phosphorylation plays a key role in prokaryotic signaling and accounts for approximately 6% of the protein phosphorylation events in eukaryotics. Phosphohistidines generally act as intermediates in the transfer of phosphate groups from donor to acceptor molecules. Examples include the bacterial phosphoenolpyruvate:sugar phosphotransferase system (PTS) and the histidine kinases found in two-component signal transduction pathways. The latter are utilized by bacteria and plants to sense and adapt to changing environmental conditions. Despite the importance of histidine phosphorylation in two-component signaling systems, relatively few proteins have so far been identified as containing phosphorylated histidine residues. This is largely due to the instability of phosphohistidines, which, unlike the phosphoesters formed by serine, threonine, and tyrosine, are labile and susceptible to acid hydrolysis. Nevertheless, it is possible to preserve and identify phosphorylated histidine residues in target proteins using appropriate sample preparation, affinity purification, and mass spectrometric techniques. This chapter provides a brief overview of such techniques, describes their use in confirming histidine phosphorylation of a known PTS protein (HPr), and suggests how this approach might be adapted for large-scale identification of histidinephosphorylated proteins in two-component systems.[27]identification of histidine phosphorylations 549
The paper deals with the issue of maintenance and renovation of cultural heritage objects. This is a very specialised area of cost optimization, for which there can still be used procedures and methods applied to more normal contemporary objects, but where there are many peculiarities and differences that need to be taken into consideration. In the initial phase, it is necessary to gather all relevant data about such objects. From data there can be obtained information that can be used to build the structure and correlations of the recovery and maintenance model. In the Heritage Catalogue there can be found basic information about cultural heritage objects. It provides basic description of the objects, but technical data which could be used for creating the recovery and maintenance model are missing. Only if based on a sufficiently large and properly structured database, is it possible to deduce the correlations and dependencies needed to create a system for the types of planning and optimization involved in recovery and maintenance. In order to establish the recovery and maintenance costs, it is necessary to complement the database for individual construction elements costs and the length of recovery and maintenance cycles.
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